This invention relates to a sheet stripping device for stripping off the peripheral surface of a rotating drum a sheet which is maintained in intimate contact with a specific zone of the peripheral surface of the drum.
In one type of electrophotographic copying apparatus, the photosensitive layer made of a photoconductive material and provided on the peripheral surface of a drum is electrically charged in its entirety by a corona discharge, the charged photosensitive layer is exposed to an optical image of an original to be duplicated to form an electrostatic latent image thereon, and a visible toner image is formed by causing toner particles to adhere to the electrostatic latent image. A copy sheet is brought into pressing engagement with the peripheral surface of the drum to produce a duplicate of the visible toner image on such copy sheet by transfer printing, and the duplicate of the toner image is fixed so that a copy of the original can be produced.
In one method known in the art, the copy sheet brought into pressing engagement with the peripheral surface of the drum is stripped off the peripheral surface of the drum by blowing a stream of air between the copy sheet and the peripheral surface of the drum. This method has the disadvantage of the toner image formed on the copy sheet disintegrating because the toner particles are blown off the sheet by the air. In another method known in the art, sheet pick-off means comprising a plurality of sheet pick-off claws is actuated in synchronism with the rotation of the drum to bring the front ends of the claws into engagement with the peripheral surface of the drum when the leading end of each copy sheet adhering to the drum comes to a point at which the sheet is to be stripped off the drum. Some disadvantages are associated with this method. The copying apparatus must be additionally provided with a synchronizing device so as to actuate the sheet pick-off means synchronously with the drum. Since the sheet pick-off means is brought into engagement with the peripheral surface of the drum, the photosensitive layer on the latter tends to become damaged.